The goal of this research is to gain insight into how language learners are able to form multiple representations when exposed to more than one language. Previous research has conflicted with respect to the age at which this ability is present (see Sebastian-Galles & Kroll, 2003). The proposed investigation will span infant and adult learners in order to understand whether the ability to form multiple representations is available to infants at 10 months of age and whether there are changes in processing over the course of development. Previous perceptual research investigating the development of bilingual language acquisition has typically focused on infants' abilities to discriminate between two different languages. The research proposed here employs a speech stream segmentation task that more directly assesses whether listeners are capable of forming multiple representations. Specifically, the experiments are designed such that participants must form separate representations for 2 artificial "languages" in order to correctly parse the languages and correctly identify the "words". Thus, this research also addresses a critical problem for the statistical learning literature. Namely, how can language learners correctly segment the input from multiple languages? If the statistics are combined across languages, incorrect segmentation of both languages could occur. A second goal of this research is to investigate the acoustic cues that may facilitate the formation of multiple representations. Language learners may face a difficult task of trying to determine when they are in the presence of multiple languages. Therefore, the task of the learner is to identify relevant features that denote a language change. In the proposed experiments, a series of cues will be manipulated in an effort to determine which features may be useful for cuing language learners to the presence of multiple languages. In sum, the proposed research will fill gaps in current knowledge regarding both bilingual language acquisition as well as statistical learning.